1. Field of the Invention
This invention relates to an apparatus having dialing means performing a calling operation based on telephone number data, and more particularly an improvement in and relating to a dialing system of such apparatus.
2. Description of the Prior Art
Facsimile apparatus having a dialing performance are now used extensively. Among such facsimile apparatus is included a facsimile apparatus having abbreviated dialing functions. In such facsimile apparatus, the telephone number data of the facsimile apparatus of called parties or offices to which calling is frequently made is stored previously and the stored data are converted into a read out selection signal (dial signal) by, for example, three key operations such as "#10". The selection signal thus formed is sent out to a telephone line (office line). This system enables calling without making a dialing operation corresponding to the telephone number of the facsimile apparatus of a called party by using a telephone set which uses telephone lines in common with the facsimile apparatus. Thus, it is advantageous that the number of mistaken telephone calls can be reduced, and the operation can be simplified. Even in a facsimile apparatus having an ordinary manual dialing function instead of the abbreviated dialing function, dialling operation can be made by a dial provided in the facsimile apparatus instead of using a separate telephone set. Thus, there is an advantage that the dialing operation can be made readily.
However, it is found that such facsimile apparatus as described above has the following disadvantages.
More particularly, most of the existing facsimile apparatus has simple transmitting and receiving functions in addition to additional functions such as a copying function. In such facsimile apparatus, interruption cannot be made for a central processing unit (CPU) that controls the overall operation to perform a different operation by additional function during transmitting and receiving operation. This is because during the operation as a copying machine, a recording unit and a read out unit are in operation so that when an operator wants to effect transmission and reception, the recording unit, the read out unit, a data bus, etc. are being used. Therefore, the CPU cannot permit transmission and reception operations. For this reason, an interruption for other operations is inhibited. In this case, even when the CPU is set in an automatic receiving mode, the telephone set and the telephone lines are connected to each other.
For this reason, when facsimile apparatus of a calling party receives a calling signal during the operation of an additional function, although the telephone set connected to the lines generates a call tone, since the CPU of the facsimile apparatus inhibits interruption based on a calling detection (calling signal detection), it is impossible to effect an operation in accordance with a calling detection until the operation by the additional function is completed. As shown in FIG. 9, the calling detection is made by detecting a call signal a which is an intermittent signal of a predetermined frequency sent out from a telephone exchange to the telephone lines, and each time a signal of the predetermined frequency is detected, a detection signal b is inputted to the CPU. Then, in response to this detection signal b, the CPU judges that there is a calling signal. In FIG. 9, T.sub.1 represents a period in which the signal of the predetermined frequency appears (on period), T.sub.2 a period in which the signal does not appear (off period), and T.sub.3 a period in which the call signal a is repeated. When the operation of the additional function terminates at point A, as the detection signal b is inputted at that point (that is the H level), the CPU can effect calling detection but at point B since no detection signal is inputted (that is at a L level), calling detection is impossible. Consequently, when a calling request is made by an abbreviated dialing operation, regardless of the presence of the calling signal, the CPU will send out the selection signal after it has accessed the line. In other words, even though the state has changed to the receiving state, the calling operation will be made, thereby causing abnormal transmission and reception which results in decrease in the efficiency of using the lines, decrease in the efficiency at the line of repeated operations, and decrease in the reliability of the apparatus.